Provided is a combustion experiment device (1), which includes a reaction tube (2) into which a sample fluid (X) flows and to which a temperature gradient in which a temperature rises toward a downstream side is imparted, and a burner part (4) that is configured to flow a combustible gas (Y) along and around the reaction tube from the downstream side to an upstream side of the reaction tube and to maintain a flame (F) surrounding the reaction tube from the outside in a radial direction of the reaction tube.